Mechanics of the New UWA Robot

Abstract

This contribution presents the dynamics modelling method suited to solving both the inverse and direct problems for parallel robots. The method is based on the application of Hamilton's canonical equations in carefully chosen dependent coordinates , called the extended space. The appropriateness and effectiveness of the method is presented by solving the dynamics of the New University of Western Australia Robot-NUWAR. NUWAR, described in detail during 1999 ACRA in Brisbane, is a variation of the well-known Delta parallel robot, having a maximum workspace volume. It is shown that the proposed method is numerically more efficient that the more traditional acceleration-based ones (e.g. Lagrange and Newton-Euler). Hamilton's equations do not require accelerations as input data to the inverse dynamics algorithm. This results in the better accuracy of the algorithm. The solution of the forward problem of dynamics was obtained without any difficulties by transforming the original system of differential-algebraic equations of index 2 to ordinary differential equations and using a standard stepping algorithm with Baumgardte stabilisation.